Note: Descriptions are shown in the official language in which they were submitted.
CA 02625254 2008-04-08
Bone regeneration element
The invention relates to a bone regeneration element for tooth implantation.
In dental implantology, artificial tooth roots which usually are made of
titanium or the
like, are fixed in the jawbone, e.g. by screwing them into place. The
artificial root of the
tooth and the dental implant, respectively, will then support the artificial
structure such as
e.g. the artificial crown of the tooth or the replacement tooth. For cases
where the quantity
of the existing bone substance is insufficient for fixing the artificial root,
it is known to
effect a corresponding osteogenisis e.g. by implantation of autologous bone
which is taken
from the hip bone, for instance. Such an approach involves a difficult and
time-consuming
surgical intervention e.g. on the hip. A procedure of this type cannot be
performed directly
in a conventionally equipped dentist's office.
It is an object of the invention to provide a bone regeneration element which
is suited to
enhance a controlled osteogenisis directly around the artificial root of the
tooth and around
the implant, respectively.
According to the invention, the above object is achieved by the features
indicated in
claim 1.
The bone regeneration element of the invention serves for the formation of
bones which
subsequently will be used to hold an artificial root or an implant. For this
purpose, the
bone regeneration element comprises an annular body shaped as a ring segment
or an
annular body shaped as a full ring. This ring-segment-shaped or full-ring-
shaped body is at
least partially made of a porous material. For osteogenisis of the artificial
root, the bone
regeneration element of the invention is arranged on the jawbone in such a
manner that the
element will at least partially surround the artificial root. To accomplish,
with the aid of
the bone regeneration element, a long-term stabilization of the artificial
root or the implant
by use of newly formed bones, a gap or filling space existing between the bone
regeneration element and the artificial root will be filled with filling
material. Depending
on its nature and dimension, the bone regeneration element alone or in
combination with
the filling material is already effective to improve a primary stability which
will enhance
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CA 02625254 2008-04-08
an osseointegration of the artificial root and respectively the tooth implant
as well as the
new formation of bone around the artificial root, and which further will
establish the
precondition for the durable secondary stability.
The filling material is a synthetic or natural bone replacement material; this
material can
be biologically inert or bioabsorbable. Suitable as synthetic filling
materials are e.g.
calcium phosphates such as hydroxylapatite, tricalcium phosphate, bioactive
glasses
and/or calcium sulfates. Also mixtures of these materials, such as e.g.
biphasic calcium
phosphates, can be of particular usefulness. A natural filling material can be
of human or
xenogeneic origin; particularly it can be an autologous bone transplant which
is obtained
extra-orally or intra-orally. Further, use can be made of bone materials of
other origins
which are suitable for thus application. Autologous bone materials can be
prepared of
bone chips or be available in ground form or as a bone block. Suitable as
natural filling
materials are e.g. bone materials from the chin, from the retromolar jaw
region, from the
upper jaw, from the nasal thorn, from the iliac crest and from the skull cap
as well as
bovine materials, algae or corals as well as collagens. All of these materials
can also be
combined with each other in a suitable manner and, if required, will be mixed
with liquids
such as e.g. the patient's own blood or bone marrow. Preferably, use is made
of a mixture
of bone chips or bonemeal and the patient's own blood. It is a common feature
of the
above mentioned filling materials that, because of their composition, they are
effective to
enhance the regeneration of new bone structures.
Due to the porosity of at least a part of the ring-segment-shaped or full-ring-
shaped
annular body and due to the provision of suitable filling material which
preferably consists
of endogenous substances, osteogenisis around the artificial tooth root and
the tooth
implant, respectively, is enhanced, while vessels can sprout into the relevant
region
through the porous material. This sprouting of vessels is the precondition for
the
generation of bones and respectively the integration of the ring-segment-
shaped or full-
ring-shaped annular body into the newly formed bone. As a result, the ring-
segment-
shaped or full-ring-shaped annular body will be integrated into the newly
formed bone and
thus will be stabilized. Accordingly, in the process, the artificial tooth
root and the tooth
implant, respectively, is integrated into the newly generating bone
(osseointegration).
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Conventionally, in the bone formation process for implanting an artificial
tooth root, use is
made of a filler material which partially consists of autologous bone
material. In case of an
implanting in the posterior maxilla, there may be used, e.g. for the so-called
sinus floor
elevation, a very large augmentation volume and thus a large quantity of
filling material.
In the presently described method, by contrast, a much lower volume of filling
material is
required since only the region between the ring-segment-shaped or full-ring-
shaped body
and the artificial tooth root has to be filled with filling material. Thus,
according to the
invention, the transplant quantity of autologous bone material can be
considerably
reduced, thus rendering it possible to abstain more frequently from extra-oral
bone
generation.
By way of a further example, the ring-segment-shaped annular body can be used
primarily
in the anterior region both of the maxilla and of the mandible for bone
regeneration in case
of loss of the vestibular bone lamella. In doing so, the ring-segment-shaped
body serves
for reducing the required quantity of filling material and for stabilizing the
filling material
around the exposed tooth implant which had been safely anchored by its apical
region in
the residual bone. This application makes it possible to reconstruct an
aesthetic jaw ridge
profile.
Further, the inventive intervention can be performed by way of a mere
outpatient
treatment in any conventionally equipped dentist's office; this is made
possible because in
intra-oral bone generation, only local anesthesia is needed and in most cases
an extra-oral
generation of bone material can be omitted.
The bone regeneration element of the invention offers the particular advantage
that the
surrounding area of the tooth implant can be exactly defined. Particularly,
the intermediate
or filling space is limited and the filling quantity is thus clearly defined.
Especially, the
filling quantity is noticeably reduced as compared to conventional methods.
Preferably, the inventive annular body comprises a body shaped as a ring
segment or a
body shaped as a full ring. This body will thus be a tubular body or a tube-
segment-shaped
body formed in the manner of a hollow cylinder or a hollow-cylinder segment.
In such a
configuration, the annular body is preferably circular or is formed as a
segment of a circle
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but can also have a polygonal shape. Particularly, the outer contour of the
ring-segment-
shaped or full-ring-shaped body can have a shape which has been adapted or is
adaptable
to the given conditions. For instance, an adapting process can be performed on
the ring-
segment-shaped or full-ring-shaped body on the basis of the residual natural
bone still
existing in the immediate vicinity.
Preferably, however, the ring-segment-shaped or full-ring-shaped body is a
circular body
or a body formed as a partial circle.
To effect a reliable sprouting of the vessels, the annular body is, at least
within ring
segments, made of a porous material throughout the wall thickness. The porous
material
thus extends from an outer wall all the way to an inner wall of the annular
body, thus
allowing a sprouting of the vessels from the outside to the inside into the
filling material.
Particularly in case of ring-segment bodies, it is not required for the porous
material to
extend through the whole wall thickness, since a sprouting of vessels is
possible also via
the lateral opening of the ring-segment-shaped body. The porosity of the
material will in
this case serve particularly for stabilizing the ring-segment-shaped body and
or the
artificial tooth root and respectively the tooth implant by sprouting of
vessels or by new
formation of bones. This applies particularly to bodies shaped as full rings
since the
vessels will then be allowed to grow also the axial direction from the jaw
bones into the
filling material. Also with regard to this process, the porosity of the
material serves for
fixing the annular body and of the artificial tooth root and respectively the
tooth implant
by the sprouting of vessels into the porous material, and for a new formation
of bones.
The mechanical strength of the full ring-shaped or ring-segment-shaped body is
influenced
above all by the composition of the body. What is important is a certain
degree of
porosity; good results are obtained by an overall porosity of 20% to 80%. The
range from
30% to 70% is preferred, while the range from 40% to 60% is especially
preferred. The
pores are interconnected throughout the cross section of the body in order to
guarantee an
open connection for inward-growing cells and diffusing nutrients, gases and
liquids
between the inner and outer sides of the body.
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To still further improve the good connection between the forming new bone
material and
the annular body, an inner wall and/or an outer wall of the annular body have
a high
roughness. This is effective to improve the osteoconductivity.
Further, particularly the surface of the inner wall and, if required, also of
the outer wall is
enlarged. Also in this manner, the firm hold of the annular body in the newly
generated
bone is improved by increased osseointegration.
If the annular body is shaped as a full ring, the inner diameter has to be
adapted to the
outer diameter of the artificial tooth root in such a manner that the
intermediate space is
sufficiently wide for insertion of a filling material into it, a preferred
width being in the
range of 1- 2 mm. The wall thickness and the height of the full-ring-shaped
body are
selected such that the osseointegration of the artificial tooth root and of
the tooth implant,
respectively, is made possible. The wall thickness is preferably selected in
the range of 1-
2 mm and/or the height is preferably selected in the range of 3 - 7 mm. A ring-
segment-
shaped body will preferably have corresponding dimensions.
With particular preference, the ring-segment-shaped or full-ring-shaped
annular body is
provided with a bearing element so that a plurality of annular bodies,
particularly two
annular bodies, can be arranged in a simple manner with exact positional
accuracy relative
to each other. Thus, for instance, two annular bodies can be arranged onto
each other with
exact positional accuracy. Position-defining elements can comprise e.g. a
projection
formed on one annular body that is configured for form-locking engagement with
a recess
formed on a second annular body. Also, a preferably annular groove can be
provided to be
engaged by a likewise annular spring of the second annular body. It is
particularly
preferred if the position-defining elements are arranged on mutually
confronting end faces
of the ring bodies.
Particularly for fixation of ring bodies on massively receded bones, the
annular body is
preferably connected to a holding element. The holding element is e.g. a
clamping
member such as a clamping screw or a clamping nut, for instance. In cases
where the still
available natural bone structure is very small, a bone regeneration element
fitted with a
holding or clamping element can establish the required primary stability of
the artificial
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tooth root. In the present embodiment, the lower annular element comprises a
screw thread
and/or has a larger outer diameter. The screw thread or a clamping element are
effective to
lend the bone regeneration element a firm seat on the artificial tooth root. A
larger
diameter of the lower annular element will increase the abutment area and thus
the
positional stability of the artificial tooth root in the residual bone. A bone
regeneration
element of the above design is distinguished - apart from the above advantages
- by an
improved primary stability of the overall system encompassing the bone
regeneration
element, the artificial tooth root, the filling material and the natural
residual bone.
As a material for producing the ring-segment-shaped or full-ring-shaped body
which is
preferably made of a porous material, there is suited e.g. biologically inert
material such as
titanium, for instance. Further, use can be made of biodegradable materials
such as e.g.
polylactide/glycolide mixtures, polyanhydrides, chitosan reinforced by calcium
phosphate
cements, or calcium phosphates such as e.g. hydroxylapatite or tricalcium
phosphate as a
base material. Further still, concerning the materials in question, reference
may be made to
the base materials which were mentioned for the filling material. Like the
filling material,
also the material of the ring-segment -shaped or full-ring-shaped body should
be capable
of enhancing the new formation of bone structures. Due to the shaping function
or
container function of the ring-segment-shaped or full-ring-shaped body, the
use of freshly
removed natural bone material is less eligible. In order to nonetheless be
able to enhance a
new formation of bones in the region of the ring-segment-shaped or full-ring-
shaped body,
a combination of the material of the body with osteoinductive substances can
be of
particular advantage. Examples of such substances are growth-stimulating
factors,
hormones or adhesive molecules.
Bone regeneration elements complemented in this manner are effective, apart
from the
stabilizing function, to function as a bone growth matrix. In the process, the
osteoinductive
substances mentioned by way of example can be released or remain tightly
connected to
the bone regeneration element.
Since the filling material preferably comprises bone meal or bone chips mixed
with the
patient's own blood and since, because of the inventive provision of the ring-
segment-
shaped or full-ring-shaped body, only small quantities of filling materials
are required, the
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bone chips obtained during the drilling of the residual bone and thus being
available for
the insertion of a part of the artificial tooth root, will already be
sufficient. Should the
quantity of bone meal or bone chips obtained in the process not suffice, bone
material can
be obtained from adjacent regions by scraping or the like, i.e. without the
necessity of a
further intervention.
The invention also relates to a bone regeneration system comprising an
artificial tooth root
made e.g. of titanium, as well as at least one bone regeneration element as
described
above. Preferably, the bone regeneration element additionally comprises a
filling material
to be introduced into the filling space. This filling material can be mixed or
enriched with
blood and bone meal/chips of the patient.
A preferred embodiment of the invention will be explained in greater detail
hereunder with
reference to the drawings.
In the drawings -
Fig. 1 is a schematic side view of an artificial tooth root inserted in a bone
and
surrounded by bone regeneration elements according to the invention,
Fig. 2 is a schematic plan view of a body shaped as a full ring,
Fig. 3 is a schematic plan view of a body shaped as a ring segment,
Fig. 4 is a schematic sectional view of an artificial tooth root inserted into
a bone, with
the root partially surrounded by filling material stabilized with the aid of a
ring-segment-
shaped bone regeneration element, and
Fig. 5 a schematic plan view of the artificial tooth root shown in Fig. 4
together with a
bone regeneration element and filling material as seen in the direction
indicated by arrow
V in Fig. 4.
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For stabilizing an artificial tooth root 10, a bore 14 will be generated in a
residual bone 12
(Fig. 1), and a cylindrical portion 16 of the tooth root will be screwed into
this bore.
Subsequently, the dental prosthesis is screwed or fastened to a likewise
cylindrical portion
18 which preferably has a smaller diameter and is part of the artificial tooth
root or the
tooth implant or is connected to the tooth or implant.
In the illustrated exemplary embodiment, to apply the filling material 31 to
the artificial
tooth root 10, two bodies 20,22 shaped as full rings will be positioned to
surround the
region 16. In the exemplary embodiment shown, the upper full-ring-shaped body
22
comprises a projection formed as a ring segment and pointing in the direction
of the other
full-ring-shaped body 20, said projection engaging an opposite groove 26 of
the lower
full-ring-shaped body 20. Both said projection 24 and the groove 26 are
arranged on
mutually opposite end sides of the full-ring-shaped bodies. In this manner,
the position of
the two full-ring-shaped bodies 22,20 relative to each other is defined.
The full ring bodies 20,22 are arranged within the maxillary sinus 23.
Between the inner walls 28 of the ring bodies 20,22 and the region 16 of the
artificial tooth
root 10, a filling space 30 is formed. This filling space 30 will be filled
with filling
materia131 comprising preferably bone meal or bone chips as well as blood of
the patient.
Since the full ring bodies 20,22 preferably completely consist of porous
material, tissue
will sprout through the full ring bodies into the filling space 30, thus
effecting a good
fixation of the full ring bodies 20,22 as well as the artificial tooth root in
the bone 12.
To make it possible, in the extremely thin residual bone 12, to obtain a
certain degree of
stability already before the formation of the new bone tissue, the
regeneration element - in
the illustrated example the regeneration element 20 - which is provided
adjacent to bone
12 can be fixedly connected to the tooth implant 10. In this case, the
relevant region will
be left without a filling space 30, preferably completely. The connection can
be realized
by clamping or by threaded engagement.
The annular bodies 20,22 can be bodies shaped as full rings (Fig. 2) but also
bodies 34
shaped as ring segments (Fig. 3).
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The ring-segment-shaped or full-ring-shaped body is preferably completely made
of
porous material. However, it can also be provided that only partial regions,
particularly
annular segments 32, consist of porous material.
In reference to a further preferred embodiment of the invention (Figs. 4 and
5), identical or
similar components will be identified by the same reference numerals.
This exemplary embodiment relates to the arrangement of a tooth implant 10 in
a bone
which is not - as described in connection with Fig. 1- too thin but is too
narrow or
includes a recess 36. Projecting from bone 36 is a part of the tooth implant.
The tooth
implant is surrounded by a ring-segment-shaped bone regeneration element 38
which
corresponding to the above described regeneration elements is made of a porous
material
or includes porous material. The shape of the regeneration element 38 is
adapted to the
recess 36. Such recesses will generally have the shape illustrated in Fig. 5.
With the aid of
normally just slight adaptations performed on the recess 36, it is rendered
possible to use
standardized regeneration elements 38. In the illustrated exemplary
embodiment, the
regeneration element 38 is a ring segment of a part-frustoconical shape. The
insertion of
filling materia131 into the filling space 30 is performed as described in the
context of the
exemplary embodiment according to Fig. 1.
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